Schematic of farm environment using co-management approach for food safety and environment.

In 2006, a deadly Escherichia coli O157:H7 outbreak in bagged spinach was traced to California’s Central Coast region, where >70% of the salad vegetables sold in the United States are produced. Although no definitive cause for the outbreak could be determined, wildlife was implicated as a disease vector. Growers were subsequently pressured to minimize the intrusion of wildlife onto their farm fields by removing surrounding non-crop vegetation. How vegetation removal actually affects foodborne pathogens was unknown. Researchers at UC Berkeley (including Daniel Karp and Claire Kremen of BFI's Center for Diversified Farming Systems), UC Davis, the Nature Conservancy, and the Natural Capital Project found that removal of non-crop vegetation did not in fact reduce incidences of enterohemorrhagic E. coli(EHEC). The study actually found a slight but significant increase in pathogen prevalence where non-crop vegetation had been removed, calling into question reforms that promote vegetation removal to improve food safety.

The results were published this week in the Proceedings of the National Academy of Sciences.
 
For their review, the researchers combined a fine-scale land use map with three datasets comprising ∼250,000 EHEC, generic E. coli, and Salmonella tests in produce, irrigation water, and rodents to quantify whether seminatural vegetation surrounding farmland is associated with foodborne pathogen prevalence in California’s Central Coast region.
 
These findings raise important research and policy considerations. According to study co-author Claire Kremen, PhD, Faculty Co-director of the Berkeley Food Institute, “California is a global leader in agriculture, and particularly fresh produce, so we have the opportunity to lead the way in responsible growing practices that do not cause environmental harm. Since removing non-crop vegetation has not been shown to reduce pathogens, it should not be promoted as part of the food safety toolkit. Instead, other promising practices should be investigated further, such as using vegetative filters to reduce pathogen contamination. Farmers can also reduce risks of pathogen contamination by growing produce that will be cooked, instead of eaten fresh, near areas where cattle and wildlife are common."
 
"Comanaging fresh produce for nature conservation and food safety" was written by Daniel S. Karp, Sasha Gennet, Christopher Kilonzo, Melissa Partyka, Nicolas Chaumont, Edward R. Atwill, and Claire Kremen.
 
Press release from UC Berkeley News.